Avoid polluting namespace

lib/refinements/array_entropy.rb

@@ -0,0 +1,13 @@
+module ArrayEntropy
+  refine Array do
+    def entropy
+      each_with_object(Hash.new(0)) do |i, result|
+        result[i] += 1
+      end.values.inject(0, :+) do |count|
+        percentage = count.to_f / length
+
+        -percentage * Math.log2(percentage)
+      end
+    end
+  end
+end